Two parameter pulse spectroscopy has been employed to resolve multiplet structures in NMR spectra arising from heteronuclear binding. In one method an indirect technique is employed which relies upon the coherent transfer of transverse magentization between coherently coupled spin systems. In this method the transverse magnetization of the first group of resonators is transferred after a time interval t.sub.1 to a second group of gyromagnetic resonators coupled to the first group. The duration of the time interval t.sub.1 is then changed in successive transient resonances and the free induction decay of the second group is detected by sampling the free induction decay wave form in a plurality of sampling times, t.sub.2. The data S(t.sub.1, t.sub.2) from successive free induction decays is then analyzed as a function of successive values for the duration of the intervals t.sub.1, to derive gyromagnetic resonance data pertaining to said first group of resonators. It was the purpose of this prior art to achieve enhancement of indirectly observed resonance data by suppressing the directly induced components of the resonance signal. In this method any persistent magnetization due to the second group of resonators is removed and after the period t.sub.1 a transverse magnetization is directly induced in the second group of resonators and the data S '(t.sub.1, t.sub.2) is obtained and subtracted from the previously derived function S (t.sub.1, t.sub.2) to suppress the contribution of direct transverse magnetization in the first data function S (t.sub.1, t.sub.2). This method forms the subject matter of commonly assigned co-pending application Ser. No. 912,787, which is in turn a continuation of Ser. No. 843,903 now abandoned.
It is also known in the prior art to observe two-dimensional NMR spectra wherein any desired order of multiple quantum transitions are selectively prepared and detected. U.S. Ser. No. 855,508, commonly assigned with the present invention, teaches a linear combination of phase shifted data S.sub.i (t.sub.1, t.sub.2, .phi..sub.i) obtained by an appropriate sequence of pulses resulting in a set of two-dimensional data arrays which upon proper linear combinations selectively yield the desired multiple quantum transition spectra.
Aue, Bartholdi and Ernst, J. Chem. Phy., Vol. 64, No. 5, pp. 2229-2246 discuss zero and double quantum transitions in NMR experiments. Preparation of nonequilibrium initial states is there realizable by any of three exemplary pulse sequences. After a subsequent evolution period, t.sub.1, a mixing pulse is applied to transform multiple quantum transitions to single quantum transitions. The work of Aue, et al. is limited to excitation and observation of multiple quantum transitions in homonuclear systems.